This invention relates to rechargeable battery handles for apparatus, and more particularly medical instrument handles having a rechargeable battery in the handle which is adapted to be inserted into a charger for recharging of the battery when the instrument is not in use.
In recent years diagnostic medical instruments in general, and particularly ophthalmoscopes, otoscopes, retinoscopes, transilluminators and the like, have become smaller and more readily portable by use of small rechargeable batteries placed in the handle of the instrument. The provision of a charger/holding stand in which the instrument may be placed when it is not being used has also become common. This allows much greater flexibility and utilization of the instruments while maintaining them at peak operating condition by automatically charging the battery cell in the handle whenever the instrument is placed in its charging rack.
In order to permit charging of the battery in the instrument handle, one of the contacts of the battery has been allowed to project out of the bottom of the handle so that when it is placed in the charging rack, electrical contact can be made to complete the circuit through the handle for charging of the battery. This unfortunately has also led to a problem with the prior art devices in that as the instruments have become smaller and the doctor's schedule has become more compressed, doctors tend to put the instrument in their pocket when going from one examining room to another. The battery contact being exposed through the bottom of the instrument handle, when the doctor puts the instrument in his pocket, any key, loose change, pencil clip or other metallic object can short the battery contact to the case of the instrument and cause a high current discharge of the battery in the instrument handle.
Not only does this discharge the battery so the instrument is not up to full illumination power when the doctor next tries to use it, but because of the characteristics of the common Nicad rechargeable battery, a very high shorting current is produced which heats up the end of the handle, as well as the coin or the key, as the case may be, to the point that burns can be sustained when one puts their hand on the instrument to remove it from the pocket.
Various suggestions have been put forward as to special switches for disabling the charging circuit, changing the internal connections, not using the case as a conductor, and the like, but all have been rejected because of the lack of convenience and the tendency of the using physician to forget to actuate the charging mechanism when not in use, with the resultant out of service condition of the instrument when the doctor needs it.